This is my take on Hughes. I don't think this is a simple 'he did a great job/did an awful job' debate.
Of course, there was a reaction to the way he was sacked and Mancini appointed. In terms of his record, he took over in extremely unique circumstances (take over pending etc). His CV wasn't wholly decorated and he played for Utd. Those two factors made some critical of him from day one. I never gave a fuck about who he played for. Nor did I expect after the Sven ending, to appoint someone who had won league titles and competed at the top end of the CL. So it was a progress appointment. Could he help us progress further. Yes with significant investment, but taking into account all those things, especially employed by the forza-mancini brigade (needing time to build a team not just talented individuals etc). The Robinho signing was not his (he had to adapt significantly as a result) and thus I judge him overall on (a) whether he moved us forward as a football club and (b) his signings (and of course other tactical things etc).
The second season is always a better judgement - and I was pleased with the signings of Tevez, Adebayor, Toure etc, as I felt, considering we were still no where near CL football, we were signing players who should (and we should all have agreed) progressed us as a football club. The RSC one was a critical mistake. But Mancini has signed some rickets without a doubtOverall, signings like Bellamy, Tevez, Given, Zab, Kompany, De Jong, were all signings (doesn't matter whether they all played their best football under Hughes again taking into account the time it takes to settle in a new league in some cases and at a new club) with progression in mind. There were critical set backs during the second season, and some lost patience of course. Do I believe we would have finished top 4 that season. No. Top 6? Yes. Do I believe he would have then, with another season finished top 4 - million dollar question and there is a fair argument to be made for and against that.
What I do know is this - Mancini has not progressed us significantly enough in terms of further spending, and considering he had a better CV and more support. Team cohesion doesn't look any better, man management doesnt look any better, and the only reason he has been backed by the brigade for this long is because (a) he didnt play for Utd (b) he is cooler (c) with more pressure and expectation has come more paranoia and obsession with utd and the media (d) and as a result - a more seize mentality and defensiveness (stubborness) against critically engaging with what is really going on.
Hughes wasn't a real success at City - but equally he wasn't a failure. I would overall, take his signings as being more critical to our progression to date, than Mancini's for sure.